Method for centering veneer sheets in a pile

ABSTRACT

A method for centering the settling of veneers on top of each other in a veneer pile, the veneers being cut from a log by slicing and dried. A substantially horizontal pile is, freely supported and having in the lateral direction extreme limits with clearance, subjected to a horizontal swinging motion whereby the extreme limits are reduced during the swinging motion.

The object of the present invention is a method for centering sheet-likeveneers in a pile formed after drying, said veneers being separated froma log by slicing.

Sliced veneers are separated from a log as lengthwise plane-slicedlayers. Slicing permits acquiring very thin veneer used as coatingmaterial in different products leaving the wood pattern visible. Formaintaining the uniformity of the wood pattern, the veneers cutsequentially from a log are usually treated as batches per log throughthe drying and stacked to appropriate piles after the drying. There areusually a constant number of veneers in the piles.

In order to facilitate the further treatment of the veneer piles and todecrease handling damages, it is necessary to pile the veneers as wellas possible concerning their position with respect to each other. Anapparatus, the operation of which is based on positioning during thepiling step, has been used when trying to reach this target. Positioningpresents its own difficulties, particularly in guiding thin veneers oneby one to a correct position during high-speed production.

In the method according to the present invention, an operation principleis used where veneers can be set substantially centered in a pile, i.e.in a pile narrowing evenly at the opposite sides thereof At the sametime the pile will be centered with respect to the apparatus handlingit, thus facilitating the positioning of the centered pile during thefurther treatment.

The substantial characteristic features of the present invention are areapparent from the enclosed claim 1.

The invention will be described in more detail with reference to theenclosed drawing illustrating an apparatus applicable in implementingthe method of the present invention.

FIG. 1 shows a general view of the apparatus,

FIG. 2 shows an illustrative drawing of the apparatus' operation at theinitial state of the operation cycle corresponding to FIG. 1,

FIG. 3, shows an illustrative drawing of the progression of theapparatus' operation,

FIG. 4 shows an illustrative drawing of further progression of theapparatus' operation, and

FIG. 5 shows an illustrative drawing of the apparatus' operation at thefinishing step of the operation cycle.

In an illustrative situation in accordance with FIG. 1, a pile 1 formedfrom veneers sliced sequentially from a log in a lengthwise plane isbrought to the operation area of the apparatus at the beginning of theapparatus' operation cycle. In the described implementation, the veneershave been sliced from a log, dried and stacked in the slicing order, thefirst acceptable veneer being at the bottom. Depending on the diameterof the log, dozens of such piles will be formed. There is apredetermined number of veneer sheets in a pile, e.g. 24 pcs, dependingon the application the apparatus is used to execute. One way of slicingthe veneer sheets is to slice the veneer sheets in to stacks, firstly upto the mid-section of the log, and then continuing to form these stacksby turning the log after the mid-section.

The veneer pile is produced after the drying phase with a traditionalpiling apparatus producing a pile where the veneer sheets are located ontop of each other in rather random positions with respect to each other.The pile is on a conveyor 2 which has transferred the pile to theoperation area of the apparatus.

The apparatus comprises gripping arms 7, 7′ each of which is connectedto actuators 3 lowering/lifting them. The range of the lowering/liftingmotion of the gripping arms is dimensioned to extend from above the pileto below the pile. The apparatus further comprises actuators 6 and 6′coupled to the gripping arms 7, 7′, said actuators enabling the grippingarms 7, 7′ on the opposite sides of the pile to operate in a transversaldirection to the pile in pairs as to be pushed towards and pulled awayfrom each other, respectively. With this motion, the gripping elementsof the gripping arms 7, 7′ can be placed under the pile and respectivelydrawn away from below the pile.

The gripping arms 7, 7′ are articulately supported and their tilt anglecan be affected by actuators 10, 10′.

Actuators of the gripping arms 7, 7′ further include devices 5 forcausing a reciprocating swinging motion of arms, such as piston-cylinderdevices with pneumatic or hydraulic operation.

For providing the swinging motion, a crank mechanism can also be used,either so that the motion caused by an eccentric crank is directed tothe gripping arm as a direct reciprocating motion, or alternatively asan eccentric rotating motion. An advantage of the last mentioned motionalternative is that it enables to stop the motion at predeterminedpoints of rotation, so that the pile can be positioned in the apparatuswith different indentations in the grain direction of the veneers. Thus,the single veneer bundles are separated with staggered endwiserelationship in the pile formed by the bundles.

The operation of the apparatus will be described with reference todrawings from 2 to 5.

FIG. 2 shows an initial state of the apparatus' operation, where theconveyor 2 has transported a pile 1 formed from dried veneer sheetsstacked in the slicing order. Depending on the construction andoperation of the apparatus which stacked the pile, the veneers arelocated in random positions with respect to each other in the veneerplane in the pile. The gripping arms 7, 7′ have been lowered by theactuators 3 so that their gripping elements are below the veneer pile.In this step, the gripping arms located at the opposite sides of thepile are controllably driven by actuators 6 and 6′ towards each other.The gripping arms 7, 7′ are mounted in an inclined position openingupwards, slightly trailing behind the slicing progression of ahalf-log's flank shape.

Their motion towards each other to a light contact with the sheet'sedges protruding from the pile is controlled with photoelectric sensors9, 9′ monitoring the opposite edges of the pile.

After this approaching motion, the gripping arms will be somewhatdistanced from each other and the veneer pile is subjected to atransversal reciprocating shaking and swinging motion with actuators 5.The gripping arms are moved towards each other, maintaining the shakingmotion and simultaneously monitoring the pressing effect subjected tothe pile by the actuators 6, 6′. Thereby a situation according to FIG. 3is produced, where the veneers on top of each other have aligned witheach other. A part of the veneers in the pile are arched depending onthe anticipated tilt of the arms 7, 7′. Press elements 8 are lowered ontop of the pile, and the gripping angle of the arms 7, 7′ to the sidesof the pile can be tightened with actuators 10, 10 for improving theshape-up of the pile (FIG. 4), after which the gripping arms 7, 7′ aredistanced from each other as shown in FIG. 5.

In the exemplary implementation, it is assumed that the veneers from ahalf-log are stacked in the sequence of slicing. The tilting of thegripping arms 7, 7′ is meant to trail the inclination of the flankprofile of the log. The stacking sequence can also be reverse, whichmust be taken into account when adjusting the inclination direction ofthe gripping arms. The trailing of the log flank profile is not,however, necessary for the operation of the apparatus. The gripping armscan also be in a vertical position, in which case the apparatus isapplicable for handling of veneer piles sliced from a half-log,regardless of the stacking sequence, or for handling veneer sheet pilessliced from a whole log, depending on the application the apparatus isused to execute.

It is also possible to make the veneers set in a pile in theirlongitudinal direction, in other words, in the grain direction, one endbeing aligned, using an apparatus implementing the method of the presentinvention. Alignment of the log's butt end is preferred. This can beachieved by adjusting the gripping arm pair 7, 7′ supporting the buttend of the veneers to operate on a lower plane than the correspondinggripping arm pair supporting the top end of the veneers. Thereby theveneers on top of each other can slide during the initial phase of theshaking in the grain direction against a stopper mounted on theapparatus at the butt end of the veneer pile.

1. A method for centering the settling of veneer sheets on top of eachother forming a pile after drying and being separated from a log byslicing, characterized in that a substantially horizontal pile, freelysupported and having extreme limits with clearance in the lateraldirection, is subjected to a horizontal swinging motion, and that duringthe swinging motion the extreme limits are reduced.
 2. A methodaccording to claim 1, characterized in that the veneer pile is subjectedto the swinging motion as an eccentric rotating motion having anamplitude exceeding the clearance of the lateral extreme limits.
 3. Amethod according to claim 1, characterized in that the veneer pile issubjected to the swinging motion as a reciprocating motion in thereduction direction of the extreme limits, having an amplitude exceedingthe clearance of the lateral extreme limits.
 4. A method according toclaim 1, characterized in that the swinging motion is used with anamplitude of ca. 50 mm.
 5. A method according to claim 1, characterizedin that the swinging motion is used with a frequency of ca. 2 Hz.
 6. Amethod according to claim 1, characterized in that the veneer pile issupported slightly inclined in the grain direction of the veneers.
 7. Anapparatus for implementing the method according to claim 1,characterized in that the apparatus comprises at least two gripping armpairs (7, 7′) setting on the opposite sides of the veneer pile, that theapparatus comprises actuators (3) for controllably moving the grippingarms to directly support the veneer pile, that the apparatus comprisesactuating elements (6, 6′) for moving the gripping arms at the oppositesides of the veneer pile towards each other, respectively apart fromeach other, and that the apparatus comprises actuating elements (5) forcausing a reciprocating shaking motion of the gripping arms.
 8. Anapparatus according to claim 7, characterized in that the supportingplanes of the gripping arms (7, 7′) are on different heights at theopposite ends of the veneer pile (1).
 9. A method according to claim 2,characterized in that the swinging motion is used with an amplitude ofca. 50 mm.
 10. A method according to claim 3, characterized in that theswinging motion is used with an amplitude of ca. 50 mm.
 11. A methodaccording to claim 2, characterized in that the swinging motion is usedwith a frequency of ca. 2 Hz.
 12. A method according to claim 3,characterized in that the swinging motion is used with a frequency ofca. 2 Hz.
 13. A method according to claim 4, characterized in that theswinging motion is used with a frequency of ca. 2 Hz.
 14. A methodaccording to claim 2, characterized in that the veneer pile is supportedslightly inclined in the grain direction of the veneers.
 15. A methodaccording to claim 3, characterized in that the veneer pile is supportedslightly inclined in the grain direction of the veneers.
 16. A methodaccording to claim 4, characterized in that the veneer pile is supportedslightly inclined in the grain direction of the veneers.
 17. A methodaccording to claim 5, characterized in that the veneer pile is supportedslightly inclined in the grain direction of the veneers.
 18. A methodaccording to claim 9, characterized in that the veneer pile is supportedslightly inclined in the grain direction of the veneers.
 19. A methodaccording to claim 10, characterized in that the veneer pile issupported slightly inclined in the grain direction of the veneers.
 20. Amethod according to claim 11, characterized in that the veneer pile issupported slightly inclined in the grain direction of the veneers.